Add an example of bluetooth usage

[gyscos]

The current demo demonstrates how to use wifi, but not bluetooth.

Including that in the example (probably using apache nimble?) could be beneficial.

[ivmarkov]

None of us understands or uses BT in his daily activities though. Help and PRs greatly appreciated!

[sebosp]

There are well documented examples now in https://github.com/esp-rs/esp-wifi/tree/main/esp-wifi/examples